I think the post should remain in SO. Users generally remove their downvoted questions and answers to save their reputations, but a deleted post might be a genuine answer with a good solution, or a good question; thus, it should not be deleted from SO entirely.

The post should remain on SO without any info about the user who asked it. In this way, that post remains available for discussion.

Is this really necessary? How often are the actual correct answers not only downvoted, but downvoted so hard that they cause a net loss of rep?
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Pops♦Aug 25 '10 at 15:26

@MLO: there is a "vote as spam" option; they're the spam flags that @George referenced. You can click "flag" under any post to access this feature.
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Pops♦Aug 25 '10 at 15:31

@MLO, wait, I'm confused. At first I thought you were talking about answers, since you said "might be genuine answer with the solution to a question"; but you also say "The question should remain on SO." Are you asking about answers, questions or both?
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Pops♦Aug 25 '10 at 15:36